DESCRIPTION (provided by investigator): Adolescents &young adults continue to experiment with smoking with many becoming nicotine dependent. Smoking is a high risk health behavior that increases risk for numerous diseases including cancer. Understanding the genetic &environmental processes underlying smoking is the focus of the present application in response to NIH PA, 'Understanding health risk behavior change in children &adolescents'. This application will integrate psychosocial &behavior genetic disciplines. We will utilize an offspring of twins design to identify the environmental experiences that contribute to the risk for various smoking behaviors while accounting for genetic factors. Smoking behaviors include smoking milestones such as age onset to first cigarette, first dependence symptom, subjective reaction to first cigarette, &lifetime measures of initiation, regular smoking, withdrawal, cessation &nicotine dependence. The offspring of twins design is especially sensitive to detecting specified environmental influences that contribute to smoking either directly or by correlation or interaction with genetic vulnerability. The ability to use the twin-family design is afforded by existing data from 767 male twin members of the Vietnam Era Twin (VET) Registry, from 1,329 of their biological offspring (age 12-28) &793 biological mothers who participated in a Children of Alcoholics Twin (COAT) study (NIAAA11667, AA11822) in 2001. After adjusting for the COAT sampling design, (i.e. paternal alcoholism) we will create 4 primary risk groups that represent high to low genetic &high to low environmental risk based on paternal smoking status. The 4 group design will be included in tests of the environmental factors contributing to offspring smoking. Environmental factors will cover the domains of parental &offspring psychopathology, family influences (e.g. parent-child relationships) &non-family influences (peer smoking). Specific aims will test for 1) genetic influences to milestones in offspring smoking, 2) contribution of paternal &offspring psychopathology on offspring smoking behavior &3) psychosocial influences on offspring smoking behavior. Results from this application will identify environmental factors that may be influenced by intervention in the realm of addictions &cancer prevention. The strengths of the application are the availability of smoking, psychiatric data &environmental constructs that have been previously collected from twins, offspring &mothers.